Saturday, January 29, 2011
【 Weak current College 】 DVI signal transmission in multimedia solution application 】
<br> <BR> one. using DVI signal strengths: <BR> 1. provides the best image quality.. <BR> Signal in VGA display, the notebook is the highest image quality.. CPU data to be .displayed to the graphics card to be processed to form a graphics display signal (digital signal), this digital signal directly drive LCD screen, the formation of the notebook display signal, which is the most "original" signal, not. by any treatment ., and losses.. The graphics signal (digital) through the D / A conversion, the formation of RGBHV signals, transmitted to the display device subject to approval by A / D process, to re-generate the digital signal to drive LCD and other .equipment, then the signal through the D / A,. D / A conversion, resulting in bandwidth, signal to noise ratio and other losses, such as: according to Nyquist sampling theory, the maximum analog bandwidth is only half the sample clock, and .56dB signal to noise ratio is only about (quantified by 8bit) ... However, if the graphics signal (digital) through and / serial conversion, the formation of DVI output, and then transmitted through the DVI to the display device and then only .after a serial / parallel conversion, you can directly drive LCD and other equipment, this process has not been A. / D, D / A conversion, will not cause signal loss.. <BR> 2. To reduce the signal loss during .transmission.. <BR> Analog signal transmission, because of the amplitude-frequency transmission system support and support group delay, high frequency interference, power ground interference and reflection effects of severe signal loss, works to solve the above problems and the difficulty of .dealing with. large, some even can not be solved.. But not when the digital signal transmission of these problems, the biggest advantage of digital transmission and anti-interference ability can be re-regeneration, Simply put, that is, as long as .the transfer process to ensure that "0", "1" Discrimination is not an error. receiving end of the signal is correct and non-destructive, and analog transmission in the difficult problem in the digital transfer process does not exist, this .is a fundamental solution to the problem, ensure that to the display device of the signal and laptop displays the signal as. give full play to the advantages of the display device, significantly improving the overall system display.. <BR> II. DVI .signal characteristics <BR> DVI signal theory, is the graphics to be displayed in the processed digital signal and HV RGB signal combination, according to the smallest non-zero coding, each pixel by 10hit the. → serial digital signals and convert the digital .stream encoded RG.B 4 groups with the pixel clock signal in accordance with the TMDS transmission mode, the flow rate of each channel of the original code 10 times the pixel clock to 1024 × 768 × .70 resolution, for example, pixel clock is .75MHz, the clock stream is 75MHz × 10, as 0.75GHz.. DVI-general in the 0.24GHz to 1.65GHz stream between.. <BR> DVI interface definition as shown below: <BR> <BR> DVI has .DVI1.0 and DVI2.0 two standards, which DVI1.0 of which only a group of signal transmission channel (data0-data2), transmission. The maximum pixel clock image 165M, the maximum signal transmission channel stream to 1.65GHz, the highest .resolution up to 1600 × 1200 × 60.. The DVI2.0 the two groups with all the signal transmission channel (data0-data5), transfer images to a maximum pixel clock 330M, can support 1920 × 1280 resolution, support for HDMI formats, .each channel's maximum signal transmission code. flow for 1.65GHz.. There is no DVI2.0 application, so all means are talking DVI1.0 DVI standards.. <BR> DVI defined DVI-I (Integrated) and DVI-D ( .Digital) two interfaces, can be seen from the interface definition, DVI-I DVI-D is in fact an increase on the basis of analog interface.. One view is that DVI-I is only a transitional interface will eventually develop into a DVI .-D and VGA were present situation, where we do not make improper evaluation.. We introduce DVI-D interface.. <BR> Three. DVI signal transmission problems <BR> DVI signal transmission has its particularity, that is too fast .because the data stream, making the transmission distance is limited to 1600 × 1200 × 60, for example, stipulated that can be transmitted .5 meters, in the current practice, to be completed by about 7 meters to 1280 × 1024 × 70, for .example, transfer of 10 meters is feasible.. Of course, use good cables, 1024 × 768 × 75 can be spread to 13-14 meters.. In the case of single-stage transmission, the primary problem is the problem drive capability, .that solve the "walk out" of the problem, but at the same time, even the digital signal, there are also long-distance transmission signal waveform distortion deformation, namely. After transmission by increasing the drive capability, the signal waveform to a .larger distortion of the signal received by the receiving end in "0" and "1" discrimination on the error, from the display point of view, there has been "wrong point", "wrong. point" when the .show will fail too, that no longer appear.. In fact, DVI signals over long distances, as the distance increases, the display can be observed are: good wrong point → point → → more wrong to fail.. Failure may be the signal ."walk," and can not get to the monitor, it may be "can walk", but "wrong point of" too much and failed.. <BR> Therefore DVI signal cable transmission is concerned, there are .different applications.. 1, Adepter, only the drive capability to solve the problem.. Signal input through the high-frequency amplifier, the drive to ensure that their may be some distance ahead, but is not responsible for signal shaping, can be cascaded ., it is suggested no more than three MS; 2, Repeater, when the signal input. be carried out and and and → string → string conversion, the signal will be re-shaping, and then drive through the drive circuit, which is a .forward concept.. As long as the signal does not come before the distortion level to determine the error, which produces the "wrong spot" level, then the signal sent back to class and just come out the same graphics card is the right signal .to send is at 7 meters distance. (1600 × 1200), can be cascaded, and the limited number of cascade.. 3, Line Driver, the DVI signal through a balanced approach, and after Repeater plastic handle which allows it to substantially increase .the transmission distance, an optional Line Driver 35 meters transmission distance of about (1600 × 1200), if it is 1024 × 768,. up to 45 meters, and can be infinite cascade, especially the Line Driver signals back-end applications, there .is no relay power supply problems.. <BR> DVI signals can also have other means of transmission, such as cable and optical fiber, cable ways have been discussed in the article, here only cable transmission.. The current data and practice, .through the network cable, the DVI signal means in accordance with Gigabit Net newsletter to sort and transport, 1280 × 1024 × 60 50 m can be transmitted in theory, if we can use the existing transmission cable. prospects very attractive, but inside there are .several problems, one can use Gigabit Ethernet to 1280 × 1024 × 60, resolution is not high, the actual use of this can be tolerated.. However, only one channel communication signal transmission, and DVI is also passed four signals, and signals on .the bit demanding, so cable must be specific (experiment if an ordinary network cable, can only transfer 1 - .2 m), which a lot of inconvenience for practical use, can not use existing network wire DVI signals, and then taking into account .the special converter cable prices and the price, it seems not a good choice but so suitable for general. cable look after the equipment out.. <BR> Four. DVI signal transmission performance / cost evaluation <BR> DVI signal transmission distance .according to different devices should be used in different, first cable, the cable has been able to find the current point of view, generally about 7 m to transfer (1600. × 1200), then I am afraid, something never done a long, .1280 × 1024 × 60 to to 10 meters, 1024 × 768 to go to 12-13 meters, the price of 20-40 yuan / m, other, DVI connector in the system. When demanding to do the same when the cable connector in .the technology and materials to do different, and the effect of transmission distance is different, so the price of finished product lines will be quite different.. <BR> Generally not recommended in the project Adepter, because there may be "wrong point" .;, but also in the design will not advance to consider what went wrong, especially in multi-path of the occasion, as with the Repeater, simple one, and. cost is not very different.. When the distance is more than " .a standard length "when the (1600 × 1200,7 meters), can be decided according to the distance Repeater or Line Driver, the difference is that the transmission distance of a Line Driver Repeater much larger than one, but the cost difference between a .. times.. Quo's Repeater in 1800RMB, while the Line Driver in 3400RMB or so.. $ 199 international Adepter around, Repeater $ 399 or so in the current Line Driver not found a similar product.. When the distance of 100 meters, because .the cable and the Line Driver taking into account the cost of equipment is recommended to use optical transmission, especially in certain special circumstances and occasions, on the optical transmission done before the introduction of a separate later.. But with the cable and lower the cost .of forwarding devices, optical transmission will be mainly used in ultra-long haul of the occasion.. <BR> Low cost DVI DVI transmission and the emergence of switch matrix, for paving the way for the application of DVI.. <BR> .;..